WHAT DISINFECTANTS MOST EFFECTIVELY KILL BACTERIA? Bio Club 10/21/15
HOW DO DISINFECTANTS/ ANTISEPTICS WORK? Disinfectants are used on surfaces, antiseptics are used on living tissues (humans) Bactericidal: kill bacteria Bacteriostatic: stop bacterial growth but doesn’t kill Common disinfectants: alcohol, hydrogen peroxide, chlorine- based bleach, soaps, and iodine
OXIDIZING DISINFECTANTS Oxidizes molecules on bacteria’s surface Cell walls & membranes disrupt and surface proteins become damaged and start clumping Cell can’t respond to damage quickly - it splits open SODIUM HYPOCHLORITE
BACTERIAL CELL WALL & MEMBRANE
SOAPS Soap is made of fatty acids - they have a hydrophobic and hydrophilic end Hydrophobic ends suspend oils on your hand and bacteria Hydrophilic ends attach to water to wash bacteria away Regular soap does not kill bacteria, but antibacterial soaps have a compound called triclosan that disables a bacterial enzyme that makes cell membranes (humans don’t have this enzyme)
HOW TRICLOSAN WORKS Stops elongation process of fatty acid chains in plasma membrane Acts as a competitive inhibitor to the catalyst enzyme Takes up active sites and stops fatty acid chain growth, stopping cell membrane growth and killing cell
ALCOHOLS Denatures membrane proteins of bacteria and dissolves lipid membrane As membrane has hydrophobic and hydrophilic ends, adding alcohol will cause it to break apart as the hydrophilic ends are all attracted to alcohol Alcohol disrupts protein bonding/ shape - proteins not being able to function properly leads to cell death
QUESTIONS TO ANSWER Predict what will happen in each section Is the hand soap antibacterial? What about the dish soap?
QUESTIONS Is hand sanitizer usually a disinfectant or antiseptic? What about hand soap? Dish soap? Is hand sanitizer bactericidal or bacteriostatic? Why? How does hand sanitizer disinfect?
PREDICTIONS What will you see on the tray with water? With hand sanitizer? What will you see on the agar if the hand soap or dish soap contains triclosan? If the hand soap or dish soap does NOT contain triclosan, what can you expect to see on the agar?
NEXT STEPS Come in in two days to see the progress We’ll keep it in the fridge if you can’t come to check on it Answer the question of which is most effective in killing bacteria
http://www.holchem.co.uk/expertise/surface-disinfection/ disinfectants/ http://scienceline.ucsb.edu/getkey.php?key=2168 http://www.typesofbacteria.co.uk/how-do-disinfectants- antiseptics-work.html https://illumin.usc.edu/68/what-makes-antibacterial-soap- antibacterial/ http://scienceline.ucsb.edu/getkey.php?key=2160
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